Stereochemistry of α-halogeno-sulphoxides. Part III. Absolute stereochemistry of α-chlorination and α-bromination of benzyl methyl sulphoxide

Abstract

α-Chlorination and α-bromination of benzyl methyl sulphoxide by electrophilic halogenating agents in pyridine afford mixtures of benzyl halogenomethyl sulphoxide and α-halogenobenzyl methyl sulphoxide. The reactions at the methyl and at the benzylic carbon atoms proceed with retention and inversion of configuration at the sulphur atom, respectively. Only one of the two possible α-halogenobenzyl methyl sulphoxides is obtained. In the case of the (S)-sulphoxide the reaction involves selective replacement of the pro-S benzylic hydrogen atom and occurs with retention of configuration at carbon.